This invention relates to a specialized container that allows a process or method of replacing the atmospheric air that is in a container, which is composed of reactive gas species such as oxygen and water vapor, with an inert gas species such as nitrogen, carbon dioxide, argon, and the like, so that a material or the surface of the material disposed in the container does not undergo reactions such as oxidation during storage and/or transportation. Typically, the inventive container is used for the preservation of microscopy or material samples that may undergo changes during the delay between the time the sample is prepared and the time when analysis of the sample occurs, wherein the change in the sample would otherwise adversely affect the results of the analysis. It also includes the preservation of ingredient materials during delays between processing steps in the synthesis of new materials.
There are many examples in microscopy, which include optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanned probe microscopies (SPM), where the sample may change from its desired state because it is exposed to the reactive gas species in the atmosphere. For example, in optical microscopy, oxidation or reaction with sulfur in the air can lead to color changes seen on the sample that affect the quality and the interpretation of the image. SEM, TEM, and SPM techniques are surface sensitive and oxidation of the surface can lead to charging effects and/or the inability to examine the sample. The presence of a modified surface can lead to erroneous interpretation of the images or data acquired from samples that undergo changes. In fact, in some cases such as in electron beam back scattered diffraction (EBSD), the diffraction signal is so sensitive to the condition of the surface, that the changed surface could render the technique useless for the analysis.
There are a number of ways in which materials scientists preserve samples from the adverse effects of exposure of the samples to atmosphere. Moisture in air can be the major problem and an effective desiccant in an enclosed container will often prevent problems. Encapsulation in tubes that have been evacuated, backfilled with an inert gas, and then sealed have been effective. Exclusion of air by the use of a vacuum container will also solve the problem, providing that the vacuum generation process is sufficiently clean from oil and water vapor. To be effective, whatever method is used for the preservation of the samples requires that the concentration of the reactive gas species in the container holding the samples be decreased to very small values and maintained.
The major problem with these techniques is that they are not portable with respect to transporting samples and then resealing them after the sample has been examined at a remote site, unless identical apparatus are located at the two sites. For microscopy applications, samples are often moved between laboratories separated by great distances, and the available facilities and instrumentation will be different between the two locations. For example, when samples are moved to the laboratory where the analysis is to be made, a suitable vacuum pump or a supply of suitable high purity inert gas may not be readily available to re-seal the sample.
Another problem is presented when samples are stored for long periods or transported to another location. It is important to know whether the transport container has maintained its integrity and the samples have not been compromised prior to submitting them for rather costly analyses, but similar facilities for re-sealing the sample are often not available at the second location.